/*
 * @(#)Matcher.java    1.64 06/04/07
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package ext.regex2;

/**
 * An engine that performs match operations on a {@link java.lang.CharSequence
 * </code>character sequence<code>} by interpreting a {@link Pattern}.
 * <p/>
 * <p> A matcher is created from a pattern by invoking the pattern's {@link
 * Pattern#matcher matcher} method.  Once created, a matcher can be used to
 * perform three different kinds of match operations:
 * <p/>
 * <ul>
 * <p/>
 * <li><p> The {@link #matches matches} method attempts to match the entire
 * input sequence against the pattern.  </p></li>
 * <p/>
 * <li><p> The {@link #lookingAt lookingAt} method attempts to match the
 * input sequence, starting at the beginning, against the pattern.  </p></li>
 * <p/>
 * <li><p> The {@link #find find} method scans the input sequence looking for
 * the next subsequence that matches the pattern.  </p></li>
 * <p/>
 * </ul>
 * <p/>
 * <p> Each of these methods returns a boolean indicating success or failure.
 * More information about a successful match can be obtained by querying the
 * state of the matcher.
 * <p/>
 * <p> A matcher finds matches in a subset of its input called the
 * <i>region</i>. By default, the region contains all of the matcher's input.
 * The region can be modified via the{@link #region region} method and queried
 * via the {@link #regionStart regionStart} and {@link #regionEnd regionEnd}
 * methods. The way that the region boundaries interact with some pattern
 * constructs can be changed. See {@link #useAnchoringBounds
 * useAnchoringBounds} and {@link #useTransparentBounds useTransparentBounds}
 * for more details.
 * <p/>
 * <p> This class also defines methods for replacing matched subsequences with
 * new strings whose contents can, if desired, be computed from the match
 * result.  The {@link #appendReplacement appendReplacement} and {@link
 * #appendTail appendTail} methods can be used in tandem in order to collect
 * the result into an existing string buffer, or the more convenient {@link
 * #replaceAll replaceAll} method can be used to create a string in which every
 * matching subsequence in the input sequence is replaced.
 * <p/>
 * <p> The explicit state of a matcher includes the start and end indices of
 * the most recent successful match.  It also includes the start and end
 * indices of the input subsequence captured by each <a
 * href="Pattern.html#cg">capturing group</a> in the pattern as well as a total
 * count of such subsequences.  As a convenience, methods are also provided for
 * returning these captured subsequences in string form.
 * <p/>
 * <p> The explicit state of a matcher is initially undefined; attempting to
 * query any part of it before a successful match will cause an {@link
 * IllegalStateException} to be thrown.  The explicit state of a matcher is
 * recomputed by every match operation.
 * <p/>
 * <p> The implicit state of a matcher includes the input character sequence as
 * well as the <i>append position</i>, which is initially zero and is updated
 * by the {@link #appendReplacement appendReplacement} method.
 * <p/>
 * <p> A matcher may be reset explicitly by invoking its {@link #reset()}
 * method or, if a new input sequence is desired, its {@link
 * #reset(java.lang.CharSequence) reset(CharSequence)} method.  Resetting a
 * matcher discards its explicit state information and sets the append position
 * to zero.
 * <p/>
 * <p> Instances of this class are not safe for use by multiple concurrent
 * threads. </p>
 *
 * @author Mike McCloskey
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @version 1.64, 06/04/07
 * @spec JSR-51
 * @since 1.4
 */

public final class Matcher
	implements MatchResult {

	/**
	 * The Pattern object that created this Matcher.
	 */
	Pattern parentPattern;

	/**
	 * The storage used by groups. They may contain invalid values if
	 * a group was skipped during the matching.
	 */
	int[] groups;

	/**
	 * The storage used by groups. They may contain invalid values if
	 * a group was skipped during the matching.
	 */
	String[] groupNames;

	/**
	 * The range within the sequence that is to be matched. Anchors
	 * will match at these "hard" boundaries. Changing the region
	 * changes these values.
	 */
	int from, to;

	/**
	 * Lookbehind uses this value to ensure that the subexpression
	 * match ends at the point where the lookbehind was encountered.
	 */
	int lookbehindTo;

	/**
	 * The original string being matched.
	 */
	CharSequence text;

	/**
	 * Matcher state used by the last node. NOANCHOR is used when a
	 * match does not have to consume all of the input. ENDANCHOR is
	 * the mode used for matching all the input.
	 */
	static final int ENDANCHOR = 1;
	static final int NOANCHOR  = 0;
	int acceptMode = NOANCHOR;

	/**
	 * The range of string that last matched the pattern. If the last
	 * match failed then first is -1; last initially holds 0 then it
	 * holds the index of the end of the last match (which is where the
	 * next search starts).
	 */
	int first = -1, last = 0;

	/**
	 * The end index of what matched in the last match operation.
	 */
	int oldLast = -1;

	/**
	 * The index of the last position appended in a substitution.
	 */
	int lastAppendPosition = 0;

	/**
	 * Storage used by nodes to tell what repetition they are on in
	 * a pattern, and where groups begin. The nodes themselves are stateless,
	 * so they rely on this field to hold state during a match.
	 */
	int[] locals;

	/**
	 * Boolean indicating whether or not more input could change
	 * the results of the last match.
	 * <p/>
	 * If hitEnd is true, and a match was found, then more input
	 * might cause a different match to be found.
	 * If hitEnd is true and a match was not found, then more
	 * input could cause a match to be found.
	 * If hitEnd is false and a match was found, then more input
	 * will not change the match.
	 * If hitEnd is false and a match was not found, then more
	 * input will not cause a match to be found.
	 */
	boolean hitEnd;

	/**
	 * Boolean indicating whether or not more input could change
	 * a positive match into a negative one.
	 * <p/>
	 * If requireEnd is true, and a match was found, then more
	 * input could cause the match to be lost.
	 * If requireEnd is false and a match was found, then more
	 * input might change the match but the match won't be lost.
	 * If a match was not found, then requireEnd has no meaning.
	 */
	boolean requireEnd;

	/**
	 * If transparentBounds is true then the boundaries of this
	 * matcher's region are transparent to lookahead, lookbehind,
	 * and boundary matching constructs that try to see beyond them.
	 */
	boolean transparentBounds = false;

	/**
	 * If anchoringBounds is true then the boundaries of this
	 * matcher's region match anchors such as ^ and $.
	 */
	boolean anchoringBounds = true;

	/**
	 * No default constructor.
	 */
	Matcher() {

	}

	/**
	 * All matchers have the state used by Pattern during a match.
	 */
	Matcher(Pattern parent, CharSequence text) {

		this.parentPattern = parent;
		this.text = text;

		// Allocate state storage
		int parentGroupCount = Math.max(parent.capturingGroupCount, 10);
		groups = new int[parentGroupCount * 2];
		groupNames = new String[parentGroupCount];
		locals = new int[parent.localCount];

		// Put fields into initial states
		reset();
	}

	/**
	 * Returns the pattern that is interpreted by this matcher.
	 *
	 * @return The pattern for which this matcher was created
	 */
	public Pattern pattern() {

		return parentPattern;
	}

	/**
	 * Returns the match state of this matcher as a {@link MatchResult}.
	 * The result is unaffected by subsequent operations performed upon this
	 * matcher.
	 *
	 * @return a <code>MatchResult</code> with the state of this matcher
	 *
	 * @since 1.5
	 */
	public MatchResult toMatchResult() {

		Matcher result = new Matcher(this.parentPattern, text.toString());

		result.first = this.first;
		result.last = this.last;
		result.groups = (int[]) (this.groups.clone());
		result.groupNames = (String[]) (this.groupNames.clone());

		return result;
	}

	/**
	 * Changes the <tt>Pattern</tt> that this <tt>Matcher</tt> uses to
	 * find matches with.
	 * <p/>
	 * <p> This method causes this matcher to lose information
	 * about the groups of the last match that occurred. The
	 * matcher's position in the input is maintained and its
	 * last append position is unaffected.</p>
	 *
	 * @param newPattern The new pattern used by this matcher
	 *
	 * @return This matcher
	 *
	 * @throws IllegalArgumentException If newPattern is <tt>null</tt>
	 * @since 1.5
	 */
	public Matcher usePattern(Pattern newPattern) {

		if (newPattern == null) {
			throw new IllegalArgumentException("Pattern cannot be null");
		}

		parentPattern = newPattern;

		// Reallocate state storage
		int parentGroupCount = Math.max(newPattern.capturingGroupCount, 10);
		groups = new int[parentGroupCount * 2];
		groupNames = new String[parentGroupCount];
		locals = new int[newPattern.localCount];

		for (int i = 0; i < groups.length; i++) {
			groups[i] = -1;
		}

		for (int i = 0; i < groupNames.length; i++) {
			groupNames[i] = null;
		}

		for (int i = 0; i < locals.length; i++) {
			locals[i] = -1;
		}

		return this;
	}

	/**
	 * Resets this matcher.
	 * <p/>
	 * <p> Resetting a matcher discards all of its explicit state information
	 * and sets its append position to zero. The matcher's region is set to the
	 * default region, which is its entire character sequence. The anchoring
	 * and transparency of this matcher's region boundaries are unaffected.
	 *
	 * @return This matcher
	 */
	public Matcher reset() {

		first = -1;
		last = 0;
		oldLast = -1;

		for (int i = 0; i < groups.length; i++) {
			groups[i] = -1;
		}

		for (int i = 0; i < groupNames.length; i++) {
			groupNames[i] = null;
		}

		for (int i = 0; i < locals.length; i++) {
			locals[i] = -1;
		}

		lastAppendPosition = 0;
		from = 0;
		to = getTextLength();
		return this;
	}

	/**
	 * Resets this matcher with a new input sequence.
	 * <p/>
	 * <p> Resetting a matcher discards all of its explicit state information
	 * and sets its append position to zero.  The matcher's region is set to
	 * the default region, which is its entire character sequence.  The
	 * anchoring and transparency of this matcher's region boundaries are
	 * unaffected.
	 *
	 * @param input The new input character sequence
	 *
	 * @return This matcher
	 */
	public Matcher reset(CharSequence input) {

		text = input;
		return reset();
	}

	/**
	 * Returns the start index of the previous match.  </p>
	 *
	 * @return The index of the first character matched
	 *
	 * @throws IllegalStateException If no match has yet been attempted,
	 *                               or if the previous match operation failed
	 */
	public int start() {

		if (first < 0) {
			throw new IllegalStateException("No match available");
		}

		return first;
	}

	/**
	 * Returns the start index of the subsequence captured by the given group
	 * during the previous match operation.
	 * <p/>
	 * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left
	 * to right, starting at one.  Group zero denotes the entire pattern, so
	 * the expression <i>m.</i><tt>start(0)</tt> is equivalent to
	 * <i>m.</i><tt>start()</tt>.  </p>
	 *
	 * @param group The index of a capturing group in this matcher's pattern
	 *
	 * @return The index of the first character captured by the group,
	 *         or <tt>-1</tt> if the match was successful but the group
	 *         itself did not match anything
	 *
	 * @throws IllegalStateException	 If no match has yet been attempted,
	 *                                   or if the previous match operation failed
	 * @throws IndexOutOfBoundsException If there is no capturing group in the pattern
	 *                                   with the given index
	 */
	public int start(int group) {

		if (first < 0) {
			throw new IllegalStateException("No match available");
		}

		if (group > groupCount()) {
			throw new IndexOutOfBoundsException("No group " + group);
		}

		return groups[group * 2];
	}

	public int start(String groupName) {

		if (groupName == null) {
			throw new IllegalStateException("Invalid group name");
		}

		for (int groupId = 0; groupId < groupNames.length; groupId++) {
			if (groupName.equals(groupNames[groupId])) {
				return start(groupId);
			}
		}

		throw new IllegalStateException("No group found.");
	}

	/**
	 * Returns the offset after the last character matched.  </p>
	 *
	 * @return The offset after the last character matched
	 *
	 * @throws IllegalStateException If no match has yet been attempted,
	 *                               or if the previous match operation failed
	 */
	public int end() {

		if (first < 0) {
			throw new IllegalStateException("No match available");
		}

		return last;
	}

	/**
	 * Returns the offset after the last character of the subsequence
	 * captured by the given group during the previous match operation.
	 * <p/>
	 * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left
	 * to right, starting at one.  Group zero denotes the entire pattern, so
	 * the expression <i>m.</i><tt>end(0)</tt> is equivalent to
	 * <i>m.</i><tt>end()</tt>.  </p>
	 *
	 * @param group The index of a capturing group in this matcher's pattern
	 *
	 * @return The offset after the last character captured by the group,
	 *         or <tt>-1</tt> if the match was successful
	 *         but the group itself did not match anything
	 *
	 * @throws IllegalStateException	 If no match has yet been attempted,
	 *                                   or if the previous match operation failed
	 * @throws IndexOutOfBoundsException If there is no capturing group in the pattern
	 *                                   with the given index
	 */
	public int end(int group) {

		if (first < 0) {
			throw new IllegalStateException("No match available");
		}

		if (group > groupCount()) {
			throw new IndexOutOfBoundsException("No group " + group);
		}

		return groups[group * 2 + 1];
	}

	public int end(String groupName) {

		if (groupName == null) {
			throw new IllegalStateException("Invalid group name");
		}

		for (int groupId = 0; groupId < groupNames.length; groupId++) {
			if (groupName.equals(groupNames[groupId])) {
				return end(groupId);
			}
		}

		throw new IllegalStateException("No group found.");
	}

	/**
	 * Returns the input subsequence matched by the previous match.
	 * <p/>
	 * <p> For a matcher <i>m</i> with input sequence <i>s</i>,
	 * the expressions <i>m.</i><tt>group()</tt> and
	 * <i>s.</i><tt>substring(</tt><i>m.</i><tt>start(),</tt>&nbsp;<i>m.</i><tt>end())</tt>
	 * are equivalent.  </p>
	 * <p/>
	 * <p> Note that some patterns, for example <tt>a*</tt>, match the empty
	 * string.  This method will return the empty string when the pattern
	 * successfully matches the empty string in the input.  </p>
	 *
	 * @return The (possibly empty) subsequence matched by the previous match,
	 *         in string form
	 *
	 * @throws IllegalStateException If no match has yet been attempted,
	 *                               or if the previous match operation failed
	 */
	public String group() {

		return group(0);
	}

	/**
	 * Returns the input subsequence captured by the given group during the
	 * previous match operation.
	 * <p/>
	 * <p> For a matcher <i>m</i>, input sequence <i>s</i>, and group index
	 * <i>g</i>, the expressions <i>m.</i><tt>group(</tt><i>g</i><tt>)</tt> and
	 * <i>s.</i><tt>substring(</tt><i>m.</i><tt>start(</tt><i>g</i><tt>),</tt>&nbsp;<i>m.</i><tt>end(</tt><i>g</i><tt>))</tt>
	 * are equivalent.  </p>
	 * <p/>
	 * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left
	 * to right, starting at one.  Group zero denotes the entire pattern, so
	 * the expression <tt>m.group(0)</tt> is equivalent to <tt>m.group()</tt>.
	 * </p>
	 * <p/>
	 * <p> If the match was successful but the group specified failed to match
	 * any part of the input sequence, then <tt>null</tt> is returned. Note
	 * that some groups, for example <tt>(a*)</tt>, match the empty string.
	 * This method will return the empty string when such a group successfully
	 * matches the empty string in the input.  </p>
	 *
	 * @param group The index of a capturing group in this matcher's pattern
	 *
	 * @return The (possibly empty) subsequence captured by the group
	 *         during the previous match, or <tt>null</tt> if the group
	 *         failed to match part of the input
	 *
	 * @throws IllegalStateException	 If no match has yet been attempted,
	 *                                   or if the previous match operation failed
	 * @throws IndexOutOfBoundsException If there is no capturing group in the pattern
	 *                                   with the given index
	 */
	public String group(int group) {

		if (first < 0) {
			throw new IllegalStateException("No match found");
		}

		if (group < 0 || group > groupCount()) {
			throw new IndexOutOfBoundsException("No group " + group);
		}

		if ((groups[group * 2] == -1) || (groups[group * 2 + 1] == -1)) {
			return null;
		}

		return getSubSequence(groups[group * 2], groups[group * 2 + 1]).toString();
	}

	public String group(String groupName) {

		if (groupName == null) {
			return null;
		}

		for (int groupId = 0; groupId < groupNames.length; groupId++) {
			if (groupName.equals(groupNames[groupId])) {
				return group(groupId);
			}
		}

		return null;
	}

	/**
	 * Returns the input subsequence captured by the given group during the
	 * previous match operation.
	 * <p/>
	 * <p> For a matcher <i>m</i>, input sequence <i>s</i>, and group index
	 * <i>g</i>, the expressions <i>m.</i><tt>group(</tt><i>g</i><tt>)</tt> and
	 * <i>s.</i><tt>substring(</tt><i>m.</i><tt>start(</tt><i>g</i><tt>),</tt>&nbsp;<i>m.</i><tt>end(</tt><i>g</i><tt>))</tt>
	 * are equivalent.  </p>
	 * <p/>
	 * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left
	 * to right, starting at one.  Group zero denotes the entire pattern, so
	 * the expression <tt>m.group(0)</tt> is equivalent to <tt>m.group()</tt>.
	 * </p>
	 * <p/>
	 * <p> If the match was successful but the group specified failed to match
	 * any part of the input sequence, then <tt>null</tt> is returned. Note
	 * that some groups, for example <tt>(a*)</tt>, match the empty string.
	 * This method will return the empty string when such a group successfully
	 * matches the empty string in the input.  </p>
	 *
	 * @param group The index of a capturing group in this matcher's pattern
	 *
	 * @return The (possibly empty) subsequence captured by the group
	 *         during the previous match, or <tt>null</tt> if the group
	 *         failed to match part of the input
	 *
	 * @throws IllegalStateException	 If no match has yet been attempted,
	 *                                   or if the previous match operation failed
	 * @throws IndexOutOfBoundsException If there is no capturing group in the pattern
	 *                                   with the given index
	 */
	public String name(int group) {

		if (first < 0) {
			throw new IllegalStateException("No match found");
		}

		if (group < 0 || group > groupCount()) {
			throw new IndexOutOfBoundsException("No group " + group);
		}

		if ((groups[group * 2] == -1) || (groups[group * 2 + 1] == -1)) {
			return null;
		}

		return groupNames[group];
	}

	/**
	 * Returns the number of capturing groups in this matcher's pattern.
	 * <p/>
	 * <p> Group zero denotes the entire pattern by convention. It is not
	 * included in this count.
	 * <p/>
	 * <p> Any non-negative integer smaller than or equal to the value
	 * returned by this method is guaranteed to be a valid group index for
	 * this matcher.  </p>
	 *
	 * @return The number of capturing groups in this matcher's pattern
	 */
	public int groupCount() {

		return parentPattern.capturingGroupCount - 1;
	}

	/**
	 * Attempts to match the entire region against the pattern.
	 * <p/>
	 * <p> If the match succeeds then more information can be obtained via the
	 * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
	 *
	 * @return <tt>true</tt> if, and only if, the entire region sequence
	 *         matches this matcher's pattern
	 */
	public boolean matches() {

		return match(from, ENDANCHOR);
	}

	/**
	 * Attempts to find the next subsequence of the input sequence that matches
	 * the pattern.
	 * <p/>
	 * <p> This method starts at the beginning of this matcher's region, or, if
	 * a previous invocation of the method was successful and the matcher has
	 * not since been reset, at the first character not matched by the previous
	 * match.
	 * <p/>
	 * <p> If the match succeeds then more information can be obtained via the
	 * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
	 *
	 * @return <tt>true</tt> if, and only if, a subsequence of the input
	 *         sequence matches this matcher's pattern
	 */
	public boolean find() {

		int nextSearchIndex = last;

		if (nextSearchIndex == first) {
			nextSearchIndex++;
		}

		// If next search starts before region, start it at region
		if (nextSearchIndex < from) {
			nextSearchIndex = from;
		}

		// If next search starts beyond region then it fails
		if (nextSearchIndex > to) {
			for (int i = 0; i < groups.length; i++) {
				groups[i] = -1;
			}

			return false;
		}

		return search(nextSearchIndex);
	}

	/**
	 * Resets this matcher and then attempts to find the next subsequence of
	 * the input sequence that matches the pattern, starting at the specified
	 * index.
	 * <p/>
	 * <p> If the match succeeds then more information can be obtained via the
	 * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods, and subsequent
	 * invocations of the {@link #find()} method will start at the first
	 * character not matched by this match.  </p>
	 *
	 * @return <tt>true</tt> if, and only if, a subsequence of the input
	 *         sequence starting at the given index matches this matcher's
	 *         pattern
	 *
	 * @throws IndexOutOfBoundsException If start is less than zero or if start is greater than the
	 *                                   length of the input sequence.
	 */
	public boolean find(int start) {

		int limit = getTextLength();

		if ((start < 0) || (start > limit)) {
			throw new IndexOutOfBoundsException("Illegal start index");
		}

		reset();
		return search(start);
	}

	/**
	 * Attempts to match the input sequence, starting at the beginning of the
	 * region, against the pattern.
	 * <p/>
	 * <p> Like the {@link #matches matches} method, this method always starts
	 * at the beginning of the region; unlike that method, it does not
	 * require that the entire region be matched.
	 * <p/>
	 * <p> If the match succeeds then more information can be obtained via the
	 * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
	 *
	 * @return <tt>true</tt> if, and only if, a prefix of the input
	 *         sequence matches this matcher's pattern
	 */
	public boolean lookingAt() {

		return match(from, NOANCHOR);
	}

	/**
	 * Returns a literal replacement <code>String</code> for the specified
	 * <code>String</code>.
	 * <p/>
	 * This method produces a <code>String</code> that will work
	 * as a literal replacement <code>s</code> in the
	 * <code>appendReplacement</code> method of the {@link Matcher} class.
	 * The <code>String</code> produced will match the sequence of characters
	 * in <code>s</code> treated as a literal sequence. Slashes ('\') and
	 * dollar signs ('$') will be given no special meaning.
	 *
	 * @param s The string to be literalized
	 *
	 * @return A literal string replacement
	 *
	 * @since 1.5
	 */
	public static String quoteReplacement(String s) {

		if ((s.indexOf('\\') == -1) && (s.indexOf('$') == -1)) {
			return s;
		}

		StringBuffer sb = new StringBuffer();

		for (int i = 0; i < s.length(); i++) {
			char c = s.charAt(i);

			if (c == '\\') {
				sb.append('\\');
				sb.append('\\');
			} else if (c == '$') {
				sb.append('\\');
				sb.append('$');
			} else {
				sb.append(c);
			}
		}

		return sb.toString();
	}

	/**
	 * Implements a non-terminal append-and-replace step.
	 * <p/>
	 * <p> This method performs the following actions: </p>
	 * <p/>
	 * <ol>
	 * <p/>
	 * <li><p> It reads characters from the input sequence, starting at the
	 * append position, and appends them to the given string buffer.  It
	 * stops after reading the last character preceding the previous match,
	 * that is, the character at index {@link
	 * #start()}&nbsp;<tt>-</tt>&nbsp;<tt>1</tt>.  </p></li>
	 * <p/>
	 * <li><p> It appends the given replacement string to the string buffer.
	 * </p></li>
	 * <p/>
	 * <li><p> It sets the append position of this matcher to the index of
	 * the last character matched, plus one, that is, to {@link #end()}.
	 * </p></li>
	 * <p/>
	 * </ol>
	 * <p/>
	 * <p> The replacement string may contain references to subsequences
	 * captured during the previous match: Each occurrence of
	 * <tt>$</tt><i>g</i><tt></tt> will be replaced by the result of
	 * evaluating {@link #group(int) group}<tt>(</tt><i>g</i><tt>)</tt>.
	 * The first number after the <tt>$</tt> is always treated as part of
	 * the group reference. Subsequent numbers are incorporated into g if
	 * they would form a legal group reference. Only the numerals '0'
	 * through '9' are considered as potential components of the group
	 * reference. If the second group matched the string <tt>"foo"</tt>, for
	 * example, then passing the replacement string <tt>"$2bar"</tt> would
	 * cause <tt>"foobar"</tt> to be appended to the string buffer. A dollar
	 * sign (<tt>$</tt>) may be included as a literal in the replacement
	 * string by preceding it with a backslash (<tt>\$</tt>).
	 * <p/>
	 * <p> Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
	 * the replacement string may cause the results to be different than if it
	 * were being treated as a literal replacement string. Dollar signs may be
	 * treated as references to captured subsequences as described above, and
	 * backslashes are used to escape literal characters in the replacement
	 * string.
	 * <p/>
	 * <p> This method is intended to be used in a loop together with the
	 * {@link #appendTail appendTail} and {@link #find find} methods.  The
	 * following code, for example, writes <tt>one dog two dogs in the
	 * yard</tt> to the standard-output stream: </p>
	 * <p/>
	 * <blockquote><pre>
	 * Pattern p = Pattern.compile("cat");
	 * Matcher m = p.matcher("one cat two cats in the yard");
	 * StringBuffer sb = new StringBuffer();
	 * while (m.find()) {
	 *     m.appendReplacement(sb, "dog");
	 * }
	 * m.appendTail(sb);
	 * System.out.println(sb.toString());</pre></blockquote>
	 *
	 * @param sb		  The target string buffer
	 * @param replacement The replacement string
	 *
	 * @return This matcher
	 *
	 * @throws IllegalStateException	 If no match has yet been attempted,
	 *                                   or if the previous match operation failed
	 * @throws IndexOutOfBoundsException If the replacement string refers to a capturing group
	 *                                   that does not exist in the pattern
	 */
	public Matcher appendReplacement(StringBuffer sb, String replacement) {

		// If no match, return error
		if (first < 0) {
			throw new IllegalStateException("No match available");
		}

		// Process substitution string to replace group references with groups
		int cursor = 0;
		String s = replacement;
		StringBuffer result = new StringBuffer();

		while (cursor < replacement.length()) {
			char nextChar = replacement.charAt(cursor);

			if (nextChar == '\\') {
				cursor++;
				nextChar = replacement.charAt(cursor);
				result.append(nextChar);
				cursor++;
			} else if (nextChar == '$') {
				// Skip past $
				cursor++;

				// The first number is always a group number or { for group name!
				int ch = (int) replacement.charAt(cursor);

				if (ch == '{') {
					// starts group name!
					cursor++;
					ch = (int) replacement.charAt(cursor);
					StringBuilder refName = new StringBuilder();

					while (ch != '}' && cursor <= replacement.length()) {
						if (cursor == replacement.length()) {
							throw new IllegalArgumentException("Illegal group reference");
						}

						refName.append((char) ch);
						cursor++;
						ch = (int) replacement.charAt(cursor);
					}

					cursor++;
					ch = (int) replacement.charAt(cursor);

					// Append group
					String grpValue = group(refName.toString());

					if (grpValue != null) {
						result.append(grpValue);
					}
				} else {
					int refNum = ch - '0';

					if ((refNum < 0) || (refNum > 9)) {
						throw new IllegalArgumentException(
							"Illegal group reference");
					}

					cursor++;
					// Capture the largest legal group string
					boolean done = false;

					while (!done) {
						if (cursor >= replacement.length()) {
							break;
						}

						int nextDigit = replacement.charAt(cursor) - '0';

						if ((nextDigit < 0) || (nextDigit > 9)) { // not a number
							break;
						}

						int newRefNum = (refNum * 10) + nextDigit;

						if (groupCount() < newRefNum) {
							done = true;
						} else {
							refNum = newRefNum;
							cursor++;
						}
					}

					// Append group
					if (group(refNum) != null) {
						result.append(group(refNum));
					}
				}
			} else {
				result.append(nextChar);
				cursor++;
			}
		}

		// Append the intervening text
		sb.append(getSubSequence(lastAppendPosition, first));
		// Append the match substitution
		sb.append(result.toString());

		lastAppendPosition = last;
		return this;
	}

	/**
	 * Implements a terminal append-and-replace step.
	 * <p/>
	 * <p> This method reads characters from the input sequence, starting at
	 * the append position, and appends them to the given string buffer.  It is
	 * intended to be invoked after one or more invocations of the {@link
	 * #appendReplacement appendReplacement} method in order to copy the
	 * remainder of the input sequence.  </p>
	 *
	 * @param sb The target string buffer
	 *
	 * @return The target string buffer
	 */
	public StringBuffer appendTail(StringBuffer sb) {

		sb.append(getSubSequence(lastAppendPosition, getTextLength()).toString());
		return sb;
	}

	/**
	 * Replaces every subsequence of the input sequence that matches the
	 * pattern with the given replacement string.
	 * <p/>
	 * <p> This method first resets this matcher.  It then scans the input
	 * sequence looking for matches of the pattern.  Characters that are not
	 * part of any match are appended directly to the result string; each match
	 * is replaced in the result by the replacement string.  The replacement
	 * string may contain references to captured subsequences as in the {@link
	 * #appendReplacement appendReplacement} method.
	 * <p/>
	 * <p> Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
	 * the replacement string may cause the results to be different than if it
	 * were being treated as a literal replacement string. Dollar signs may be
	 * treated as references to captured subsequences as described above, and
	 * backslashes are used to escape literal characters in the replacement
	 * string.
	 * <p/>
	 * <p> Given the regular expression <tt>a*b</tt>, the input
	 * <tt>"aabfooaabfooabfoob"</tt>, and the replacement string
	 * <tt>"-"</tt>, an invocation of this method on a matcher for that
	 * expression would yield the string <tt>"-foo-foo-foo-"</tt>.
	 * <p/>
	 * <p> Invoking this method changes this matcher's state.  If the matcher
	 * is to be used in further matching operations then it should first be
	 * reset.  </p>
	 *
	 * @param replacement The replacement string
	 *
	 * @return The string constructed by replacing each matching subsequence
	 *         by the replacement string, substituting captured subsequences
	 *         as needed
	 */
	public String replaceAll(String replacement) {

		reset();
		boolean result = find();

		if (result) {
			StringBuffer sb = new StringBuffer();

			do {
				appendReplacement(sb, replacement);
				result = find();
			} while (result);

			appendTail(sb);
			return sb.toString();
		}

		return text.toString();
	}

	/**
	 * Replaces the first subsequence of the input sequence that matches the
	 * pattern with the given replacement string.
	 * <p/>
	 * <p> This method first resets this matcher.  It then scans the input
	 * sequence looking for a match of the pattern.  Characters that are not
	 * part of the match are appended directly to the result string; the match
	 * is replaced in the result by the replacement string.  The replacement
	 * string may contain references to captured subsequences as in the {@link
	 * #appendReplacement appendReplacement} method.
	 * <p/>
	 * <p>Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
	 * the replacement string may cause the results to be different than if it
	 * were being treated as a literal replacement string. Dollar signs may be
	 * treated as references to captured subsequences as described above, and
	 * backslashes are used to escape literal characters in the replacement
	 * string.
	 * <p/>
	 * <p> Given the regular expression <tt>dog</tt>, the input
	 * <tt>"zzzdogzzzdogzzz"</tt>, and the replacement string
	 * <tt>"cat"</tt>, an invocation of this method on a matcher for that
	 * expression would yield the string <tt>"zzzcatzzzdogzzz"</tt>.  </p>
	 * <p/>
	 * <p> Invoking this method changes this matcher's state.  If the matcher
	 * is to be used in further matching operations then it should first be
	 * reset.  </p>
	 *
	 * @param replacement The replacement string
	 *
	 * @return The string constructed by replacing the first matching
	 *         subsequence by the replacement string, substituting captured
	 *         subsequences as needed
	 */
	public String replaceFirst(String replacement) {

		if (replacement == null) {
			throw new NullPointerException("replacement");
		}

		StringBuffer sb = new StringBuffer();
		reset();

		if (find()) {
			appendReplacement(sb, replacement);
		}

		appendTail(sb);
		return sb.toString();
	}

	/**
	 * Sets the limits of this matcher's region. The region is the part of the
	 * input sequence that will be searched to find a match. Invoking this
	 * method resets the matcher, and then sets the region to start at the
	 * index specified by the <code>start</code> parameter and end at the
	 * index specified by the <code>end</code> parameter.
	 * <p/>
	 * <p>Depending on the transparency and anchoring being used (see
	 * {@link #useTransparentBounds useTransparentBounds} and
	 * {@link #useAnchoringBounds useAnchoringBounds}), certain constructs such
	 * as anchors may behave differently at or around the boundaries of the
	 * region.
	 *
	 * @param start The index to start searching at (inclusive)
	 * @param end   The index to end searching at (exclusive)
	 *
	 * @return this matcher
	 *
	 * @throws IndexOutOfBoundsException If start or end is less than zero, if
	 *                                   start is greater than the length of the input sequence, if
	 *                                   end is greater than the length of the input sequence, or if
	 *                                   start is greater than end.
	 * @since 1.5
	 */
	public Matcher region(int start, int end) {

		if ((start < 0) || (start > getTextLength())) {
			throw new IndexOutOfBoundsException("start");
		}

		if ((end < 0) || (end > getTextLength())) {
			throw new IndexOutOfBoundsException("end");
		}

		if (start > end) {
			throw new IndexOutOfBoundsException("start > end");
		}

		reset();
		from = start;
		to = end;
		return this;
	}

	/**
	 * Reports the start index of this matcher's region. The
	 * searches this matcher conducts are limited to finding matches
	 * within {@link #regionStart regionStart} (inclusive) and
	 * {@link #regionEnd regionEnd} (exclusive).
	 *
	 * @return The starting point of this matcher's region
	 *
	 * @since 1.5
	 */
	public int regionStart() {

		return from;
	}

	/**
	 * Reports the end index (exclusive) of this matcher's region.
	 * The searches this matcher conducts are limited to finding matches
	 * within {@link #regionStart regionStart} (inclusive) and
	 * {@link #regionEnd regionEnd} (exclusive).
	 *
	 * @return the ending point of this matcher's region
	 *
	 * @since 1.5
	 */
	public int regionEnd() {

		return to;
	}

	/**
	 * Queries the transparency of region bounds for this matcher.
	 * <p/>
	 * <p> This method returns <tt>true</tt> if this matcher uses
	 * <i>transparent</i> bounds, <tt>false</tt> if it uses <i>opaque</i>
	 * bounds.
	 * <p/>
	 * <p> See {@link #useTransparentBounds useTransparentBounds} for a
	 * description of transparent and opaque bounds.
	 * <p/>
	 * <p> By default, a matcher uses opaque region boundaries.
	 *
	 * @return <tt>true</tt> iff this matcher is using transparent bounds,
	 *         <tt>false</tt> otherwise.
	 *
	 * @see java.util.regex.Matcher#useTransparentBounds(boolean)
	 * @since 1.5
	 */
	public boolean hasTransparentBounds() {

		return transparentBounds;
	}

	/**
	 * Sets the transparency of region bounds for this matcher.
	 * <p/>
	 * <p> Invoking this method with an argument of <tt>true</tt> will set this
	 * matcher to use <i>transparent</i> bounds. If the boolean
	 * argument is <tt>false</tt>, then <i>opaque</i> bounds will be used.
	 * <p/>
	 * <p> Using transparent bounds, the boundaries of this
	 * matcher's region are transparent to lookahead, lookbehind,
	 * and boundary matching constructs. Those constructs can see beyond the
	 * boundaries of the region to see if a match is appropriate.
	 * <p/>
	 * <p> Using opaque bounds, the boundaries of this matcher's
	 * region are opaque to lookahead, lookbehind, and boundary matching
	 * constructs that may try to see beyond them. Those constructs cannot
	 * look past the boundaries so they will fail to match anything outside
	 * of the region.
	 * <p/>
	 * <p> By default, a matcher uses opaque bounds.
	 *
	 * @param b a boolean indicating whether to use opaque or transparent
	 *          regions
	 *
	 * @return this matcher
	 *
	 * @see java.util.regex.Matcher#hasTransparentBounds
	 * @since 1.5
	 */
	public Matcher useTransparentBounds(boolean b) {

		transparentBounds = b;
		return this;
	}

	/**
	 * Queries the anchoring of region bounds for this matcher.
	 * <p/>
	 * <p> This method returns <tt>true</tt> if this matcher uses
	 * <i>anchoring</i> bounds, <tt>false</tt> otherwise.
	 * <p/>
	 * <p> See {@link #useAnchoringBounds useAnchoringBounds} for a
	 * description of anchoring bounds.
	 * <p/>
	 * <p> By default, a matcher uses anchoring region boundaries.
	 *
	 * @return <tt>true</tt> iff this matcher is using anchoring bounds,
	 *         <tt>false</tt> otherwise.
	 *
	 * @see java.util.regex.Matcher#useAnchoringBounds(boolean)
	 * @since 1.5
	 */
	public boolean hasAnchoringBounds() {

		return anchoringBounds;
	}

	/**
	 * Sets the anchoring of region bounds for this matcher.
	 * <p/>
	 * <p> Invoking this method with an argument of <tt>true</tt> will set this
	 * matcher to use <i>anchoring</i> bounds. If the boolean
	 * argument is <tt>false</tt>, then <i>non-anchoring</i> bounds will be
	 * used.
	 * <p/>
	 * <p> Using anchoring bounds, the boundaries of this
	 * matcher's region match anchors such as ^ and $.
	 * <p/>
	 * <p> Without anchoring bounds, the boundaries of this
	 * matcher's region will not match anchors such as ^ and $.
	 * <p/>
	 * <p> By default, a matcher uses anchoring region boundaries.
	 *
	 * @param b a boolean indicating whether or not to use anchoring bounds.
	 *
	 * @return this matcher
	 *
	 * @see java.util.regex.Matcher#hasAnchoringBounds
	 * @since 1.5
	 */
	public Matcher useAnchoringBounds(boolean b) {

		anchoringBounds = b;
		return this;
	}

	/**
	 * <p>Returns the string representation of this matcher. The
	 * string representation of a <code>Matcher</code> contains information
	 * that may be useful for debugging. The exact format is unspecified.
	 *
	 * @return The string representation of this matcher
	 *
	 * @since 1.5
	 */
	public String toString() {

		StringBuffer sb = new StringBuffer();

		sb.append("java.util.regex.Matcher");
		sb.append("[pattern=" + pattern());
		sb.append(" region=");
		sb.append(regionStart() + "," + regionEnd());
		sb.append(" lastmatch=");

		if ((first >= 0) && (group() != null)) {
			sb.append(group());
		}

		sb.append("]");
		return sb.toString();
	}

	/**
	 * <p>Returns true if the end of input was hit by the search engine in
	 * the last match operation performed by this matcher.
	 * <p/>
	 * <p>When this method returns true, then it is possible that more input
	 * would have changed the result of the last search.
	 *
	 * @return true iff the end of input was hit in the last match; false
	 *         otherwise
	 *
	 * @since 1.5
	 */
	public boolean hitEnd() {

		return hitEnd;
	}

	/**
	 * <p>Returns true if more input could change a positive match into a
	 * negative one.
	 * <p/>
	 * <p>If this method returns true, and a match was found, then more
	 * input could cause the match to be lost. If this method returns false
	 * and a match was found, then more input might change the match but the
	 * match won't be lost. If a match was not found, then requireEnd has no
	 * meaning.
	 *
	 * @return true iff more input could change a positive match into a
	 *         negative one.
	 *
	 * @since 1.5
	 */
	public boolean requireEnd() {

		return requireEnd;
	}

	/**
	 * Initiates a search to find a Pattern within the given bounds.
	 * The groups are filled with default values and the match of the root
	 * of the state machine is called. The state machine will hold the state
	 * of the match as it proceeds in this matcher.
	 * <p/>
	 * Matcher.from is not set here, because it is the "hard" boundary
	 * of the start of the search which anchors will set to. The from param
	 * is the "soft" boundary of the start of the search, meaning that the
	 * regex tries to match at that index but ^ won't match there. Subsequent
	 * calls to the search methods start at a new "soft" boundary which is
	 * the end of the previous match.
	 */
	boolean search(int from) {

		this.hitEnd = false;
		this.requireEnd = false;
		from = from < 0 ? 0 : from;
		this.first = from;
		this.oldLast = oldLast < 0 ? from : oldLast;

		for (int i = 0; i < groups.length; i++) {
			groups[i] = -1;
		}

		for (int i = 0; i < groupNames.length; i++) {
			groupNames[i] = null;
		}

		acceptMode = NOANCHOR;
		boolean result = parentPattern.root.match(this, from, text);

		if (!result) {
			this.first = -1;
		}

		this.oldLast = this.last;
		return result;
	}

	/**
	 * Initiates a search for an anchored match to a Pattern within the given
	 * bounds. The groups are filled with default values and the match of the
	 * root of the state machine is called. The state machine will hold the
	 * state of the match as it proceeds in this matcher.
	 */
	boolean match(int from, int anchor) {

		this.hitEnd = false;
		this.requireEnd = false;
		from = from < 0 ? 0 : from;
		this.first = from;
		this.oldLast = oldLast < 0 ? from : oldLast;

		for (int i = 0; i < groups.length; i++) {
			groups[i] = -1;
		}

		acceptMode = anchor;
		boolean result = parentPattern.matchRoot.match(this, from, text);

		if (!result) {
			this.first = -1;
		}

		this.oldLast = this.last;
		return result;
	}

	/**
	 * Returns the end index of the text.
	 *
	 * @return the index after the last character in the text
	 */
	int getTextLength() {

		return text.length();
	}

	/**
	 * Generates a String from this Matcher's input in the specified range.
	 *
	 * @param beginIndex the beginning index, inclusive
	 * @param endIndex   the ending index, exclusive
	 *
	 * @return A String generated from this Matcher's input
	 */
	CharSequence getSubSequence(int beginIndex, int endIndex) {

		return text.subSequence(beginIndex, endIndex);
	}

	/**
	 * Returns this Matcher's input character at index i.
	 *
	 * @return A char from the specified index
	 */
	char charAt(int i) {

		return text.charAt(i);
	}
}
